In the lamps and lanterns industry today, a conventional ballast comprises a power capacitor, a normally closed thermosentive switch, and a resistance thermometer sensor loop, etc. The ballast has strong shock noises and high temperature. Lamps or lanterns with such ballast usually have flickers. When the lamps or the lanterns are powered, the lamps or the lanterns cannot quickly light. Meanwhile, due to the voltage of the market power is instability, the ballast and the lamps or lanterns with such ballast are easy to burn out. This causes users much losing.
A new type ballast has good improvements in some parts. The circuit of the improved ballast includes a bridge rectifier circuit 21, an electrolytic capacitive filter circuit 22, a half bridge inverter circuit 23, and an LC output circuit 24. The circuit has good improvements in reducing shock noises, controlling temperature and quickly starting lighting etc. However, there are still many problems, such as lack of abnormal states protection. The common abnormal states are for example: one of the lamps is not connected; a fluorescent lamp can not start because of its cathode damaged; the cathode is normal, but the lamp can not be activated; during the fluorescent lamp working, a cathode cannot be activated or happens rectifier function; a short circuit is caused in the starter switch, etc. The electronic ballast and the fluorescent lamp (such as T5, T8 straight pipe or the other shape of the fluorescent lamps) generally cooperate with each other to work. Once an abnormal state happens during work, the ballast will be caused damage. Severing as an independently installed electronic ballast with the lamp tube being changeable, the ballast must have the abnormal states protection function. Even if abnormal states happen, the ballast does not damage. After a new lamp tube is changed, or after the abnormal state is eliminated, the ballast can still continue working.
In other aspects, for example, abilities to resist over-voltages, suppress surge currents, prolong the lives of the lamps or lanterns, multi-loads output, enhance power factor, reduce harmonic and achieve a constant power output, etc., the existing ballast for the lamps and lanterns has many shortages.
Therefore, there is a need for an improved power-saving and stabilizing ballast to overcome these above-mentioned disadvantages.